Polygon is a polygon model, as the name implies, it is to shape the body with faces, so the sphere you create is also composed of many faces. If there are fewer noodles, it will naturally be round. If you want a polygonal sphere to look round, there are several ways:

1 By adding lines and increasing the number of faces, the ball will appear round.

2 fairing, that is, fairing, is actually adding surfaces to the model.

3 Press the number key 3 to display smoothly. If you want to switch back to normal display, please press the number key 1 again. However, the 3-key sleek display is actually just for the convenience of you to observe in one view, and only shows the sleek effect, which is not really sleek.

As for the sphere in the video you mentioned, I think it may be made of nurbs. Nurbs is a kind of nonlinear editing curve, which uses the surface generated by the curve to shape the body, so it is smooth and round even without lines. I think in the video you watched,